Centrifugal pump.



W. K. RICHARDSON. CENTRIFUGAL PUMP.

APPLICATION FILED n.zs. w13.

Patented Dec. 9, 1913.

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` WILLIAM K. RICHARDSON, OF .LEAVENNQR'I} H, KANSS.

CENTRIFUGAL AP'U'lVUE'.

` Specification let.Letters,Patent Application tiled April 23, 1913. Serial Nlo.l763,175.

To zZZ 'whomz't may concern Be itknown that I, 'Winnaar K. RiemannsoN, a` citizen of the United States, residing at Leavenworth, in the county oit Leareir worth, State of Kansas, have invented a new and useful Improvement in Centri t'ugal Pumps, of which the :following is a specifica tion.'

It does not seem tirhaye. been understood by practical pump designers, that the pres sure energy produced by an impeller ot' a centrifugal pump, is the product of the radial depthof the water subjected to centrifugal force, and its angular' velocity. For this reason no provision is made in pumpsl now in general use i'or subjecting the water to centrifugal :torce within the area of cross section oft' the intake. latents have been granted which show and describe means Within the intake ot' `a centrifugal pump for subjecting the fluid to centri'liugal Aforce, but I have found that unless the means employed be properly constructed no increased etliciency can be obtained by its employment'.

`The object ofthis invention is to utilize the area of cross section of the intake ol an impeller of a centrifugal pump, whether single or ,multiple stage, by the employment. of a screw in the eye of the runner. To accomplish this result, the diameter ot the eye of the runner, its angular' velocity, and the volume passing through it, must be known in order that the pitch of the screw and the Inumber of blades constituting the Screw may be deteri'nined, for it should be understoodthat lthere is a certain maximum pressure that may be generated and utilized clue toany rotary velocity ont' the screw, dclivering a predetermined quantity ol' fluid When properlyr designed. Otherwise the best results cannot be obtained, ior it' the pitch of the screw is too great, back pressure will be imposed upon vthe suction, and if the pitch be too fine, low elliciency will result. To ,more particularly describe my invention, I Will referto the accompanying drawings, infwhich:

Figure l is a longitudinal section through adouhle suction impeller provided with a screw 'in the eyes olf the impeller in accordny i,tart-ration, the incid-ting cas estimatingparte of the pump lacing?! Fig. is a plan view oi our ol .the are ,sho-wn in Itiig. l.`

, As illustrated in lIiig. 1, A indicates a Well known fornrof impeller of the double suction type .mounted on a shaft B to revolve therewith. Said impellery is provided on each side with an intake or eye (l surrounding the shaft B. The particular construction oi the impeller forms no part of my presentinvention, and I ieed not be'particularly described, as my invention is'lapplicw ble to any form oit impeller whether oli' the single or double suctiann type, which is adapted to subject water to centrifugal force.

ln the eye of the impeller whether it be ot' the single or double suction type, is placed a screw D, said ,screw consisting ot' a central web d forming a sleeve oi a diameter sui ticient for the reception ol" the shaft ll to which it is attached. lo the sleeve are cast projecting helical vblades 1I which are inclined toward the impeller in a direction opposite to the direction ot rotation. Said blades may overlap each other` but, their combined `surfaces must at least encompass the entire cross sectional area ol" the screw as shcavir inlltig. 2, to avoid eddying and escape of the fluid under pressure. The pitch of the screw should be so determined that twice the volume ot fluid to be `delivered will equal the calculated translator-y displacement of the screw. The calculated translatory displacement, during one minute of a screw supposed to hare blades whose ends are m radial lines, is the iroduct of the number of R. 1. M., the pitelh of the screw, and the area in cross section of so much of the tubular space surroumling theshaft which is traversed by the bladcsin their revolution as is cccupied aty any instant by a figure or ligurcs which do not orcrlap in the circumtercntial direction, containing the blade or blades, and are bounded by radial planes passing through the axis of revolution and the ends of lthe blade or blades. If a single blade, whiclrat least once encircles the shaft be used, the pitch is the axial length of the blade, and the effective area in cross section is ,the area n cross section of the entire space trayersed. It' a number of equal blades be used, which hare their corresponding ends in the same transverse plane, andwhich in the aggregate at least once encircle the shaft, the etl'cctivc area` in cross section is the area in cross section oiI the entire space trz'lvers'e'd, and the length oi the screw which is ctliectivc t'or one performance of the translatory funcf 30 tory displacement, .will produce a pressure due to centrifugal force and also. a pressure due to` impactof the fluid upon the blades, the combined pressures producing a spout-"` vtion of each blade,

neglecting overlapping vortions, is the -axial length ofthe' blades. egleqiting slip, each blafde performs Iits vtranslatory function as many times'during there are non-overlapping ,one revolution as blades, and that numbermultiplied by the vaxial vlength of the blades is equal to the i pitch and the number ofR. P. M.

cumferential length of the blades in cx#l tcess of thatrequired to once encircle the shaft would not affect the calculated trans- Alatory displacement, but would aect the pith. Therefore, in any case-in which the e y shaft is at least once encircled by the com bined circumferential I length of the blades, whatever their number, the calculated translatory displacement 'is theproduct of the area in cross 'section of the space traversed, t'hc actualdisplacement-by reducing` slip in affording a greater area ofsurface to act upon the wlter. i The object of having a screw, the calcu- Vlated translate-ry displacement of which a'pproximatelyequals twice the volume delivered, is that a pbrtion'of the fluid may be longer retained within the rotary pathof' the screw,` and thus be subjected to centrif-` ugal force 'directly as the rotary velocity of I "the-blades, and inversely .as the slip.

screw having the above calculated translaing velocity toward the bitofthe blades equal to the rotary'velocity of the blades.

' IShould the calculated translatory -displaceineii-t materially eXceedt-he volume stated,

" back pressurewould be. imposed .upon the suction. While it may be shown that this is z notit-hemaxiinum centrifugal vforce that can be generated, it isa very vclose approach tio 'theinean. For instance, the greatest cen trifu'gal force. would vbe when there is no de livery, and only kinetic energy duc to cenltrifu'oalforceof tliescrew afactor. 1l-lere.

'the'vv centrifugal f orce directly asthe an? 4gularfvelocity of the 'blades'but there are .Y other conditions to be considered. No ccnl.'

:"ccrtain vol-unie:throughout -tlic operation of tri'fi'igal pump is designed to deliver any the pui'iipf. This factor varies :is the li'ead'aiid -the lift of,thesii'ctioii,.uiid'it is also somewhat 'lhcrcforc the 'throughoutthe .general efficiency of the vq jump, nitlioiit imposing bach pressure upoiif [the surtioiil .ln designing thescreiv the volunie of fili-iid delivered :by the p'iiinp vwhilev operating. at its liest ellici-encyisfthe rated..

capaci-ty' of 'the punip.

. Any-axial .length of i ai screw desired, its pitchbeing known," will -determi ne the nuniberofoblades inthe screw.

5.53 T lic purposeof the, screw v.to producecenf` `by the screw,

.entirely encompass the vscrew and that 'bei'l of cubic inches in agallon) trifugal force of the water within the area of intake, or.- eye, of the ruimer, for forcing the fluidv in the direction of'iiow, anillior producing suctional effect.

The thcory'of operaton is follows:

.Due to rotaryY motion 'of the scre'w inthe into the space traversed fiuid,water is drawn due to cavitati'on on v4Lthc back4 side of the blades. The extent f 'caii'itatioii depends .upon the angularfveloeity. of. the

blades, and the lift-ofl th suction, `atmcs pact of the fluid upon the blades, some of which is converted into prcssurc, and .kinetic energy in .the form of centrifugal force ofl the fluid .which is convertedy into useful pres- ,sure on delivery to the impeller, From'the ,go-regoing it will be seen .that the combined urfaces of the blades of the screw should pitchwill give a calculated translatory displacement in excess of the volume 'delivered Tn'eOmputing the translatory displacement of a screw, the space occupied by the screw Atheir itself', should be taken into account.V Proper allowance should also be made in designing a screw thatis to receive fluid under eitherp'ositivehcad or Suction. i

As showing one mode of 'computing the structure of the screw, the following 'i's e.

{diei-cd :Given ascrcw 10 in dianieteiglde.l

sircdlengt-h 4, 600 revolutions per minute, delivery B264 gallons per minute, space occupied by the screw beingjneglected. .The- 'i superficial area of the cross section of a GOOR. l. M.='47l24 inches. Twice the volume 3264::6528 gallons X' 231' inches (num-` :1507968:- inches. 'l`liis..number divided by 47124:.82 iiicli'es,"i\iliich is the pitch. By dividing, theA pitch-by the dcsiredlength wcdeteimine'tlie .nuiii'ber of blades .which is, 8. A'greatcr 4miinber of blades may beeniployedin a scre'ivoftliis 'p'itch and length, but they` will not increase thc-translatory displacement of the scieiv,.asthe overlappingportions ofthe 120 blades will be a ne'iitral fzone. v The lift'ofv the suction, and high angularfvelocityifof Vthe blades, whether -dueto highspeed of rovtation, or large diameter of screw, will'-` soiiiewlnit. modify the'pitch, forwhile high` 1 .25" 'v vangular- ..velocitywvill induce-cavitation onA the back of the 'blade and therefore-suctiom' .thehigli .lift..onthe. suction prevents rapid ffiow tothebladcs:

' f y Havingthus described my.invention,- wliatfi3c A' i rated volumel desire to secure by Let- .rality of blades 1n position to deliver fluid into the'eye of said rotor and revolve therewith, said blades beinginclined toward the rotor in adirection opposite to the direction ot' rotation, and having a calculated translatory displacementapproximately twice the designerfl to pass the screw.

2. In a centrifugal machine, the combination with a rotor adapted to Subject fluid t0 pressure due to centrifugal force, of a screw mounted on a shaft coaxial with said rotor and having blades in position to deflect fluid into the eye of said rotor and with, the pitch of said screw being approximately such that twice the volume delivered past the screw according to the rated capacity of the machine is equal to the calculated translatory displacement of the screw.

l 3. In a centrifugal machine, the combination with a rotr'adapted to subject fluid to pressure due to centrifugal ltorce, of a screw mounted on a shaft coaxial with the said rotor and having blades in position to deflect fluid into the eye of said rotor, and revolve revolve theremachine, is equal to the therewith, said blades having a total circumferential length ,such that they encircle the sliaft,'tlie pitch of said screw being approximately such that twice the volume delivered past the screw according to the rated capacity of the machine, is equal to the area of the cross section oil the tubular space surrounding the shaft which is traversed by the blades in their revolution, multiplied by the pitch, multiplied by the number of revolutions.

4. In a centrifugal machine, the combination with a rotor adapted to subject fluid to 4pressure duc to centrifugal force, of a screw in position to deliver fluid into the eye 3f said rotor and revolve therewith, the number oit' blades being equal to the pitch divided by the length of the screw, said. blades having a total circumferential length, such That they encircle the shaft, the pitch of said screw being approximately such that twice the volume delivered past the screw according to the rated capacity ofthe calculated translatory displacement of the screw.

WILLIAM K. RICHARDSON.

Witnesses:

I'lownLL BAn'rLii, (l. lV FowLiin. 

